Suppose the Quantity of Burgers Is Measured on the Horizontal

Suppose the quantity of burgers is measured on the horizontal axis and the quantity of bags of French fries is measured on the vertical axis.The marginal rate of substitution for burgers is

A) the ratio of burgers consumed to bags of fries consumed.
B) the ratio of bags of fries consumed to burgers consumed.
C) the rate at which a person is willing to give up burgers to get more bags of fries while staying on the same indifference curve.
D) the rate at which a person is willing to give up bags of fries to get more burgers while staying on the same indifference curve.
E) the number of burgers consumed minus the number of bags of fries consumed.